“Can the digital "signal" be over-laundered, unlike money?”
Yes!!! And this is not limited to audio :-)
As with anything else in life, striking a ‘balance’ is the key. IME, careful selection of fewer high quality components and ‘sensible’ tweaking will always yield to superior sound vs. plethora of sub par components and ‘band-aid’ tweaks.
I subscribe to everything matters philosophy so efficacy of any single component or tweak squarely depends on rest of your system. A high quality ethernet switch or external re-clocker device is not going to magically transform your digital streaming if as an example there is a laptop, node 2 or mac-mini type of component ahead in the chain.